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April 19, 2011 -- Epilepsy that is difficult to treat may be more common in those with autism than previously believed, new research suggests.

"In general, we knew prior to this study that people with autism have significantly elevated rates of epilepsy," says researcher Orrin Devinsky, MD, professor of neurology, neurosurgery, and psychiatry at the New York University School of Medicine. Devinsky is also director of the NYU Comprehensive Epilepsy Center.

In his new research, he found that epilepsy in autism is often treatment-resistant. ''Among those with autism who have epilepsy, in many cases it is difficult to control with medication,'' he says. In the small study, about 55% of those with sufficient data available had treatment-resistant epilepsy, he tells WebMD.

The research is published online in the journal Epilepsia.

It follows research published last week in the Journal of Child Neurology finding those with both autism and epilepsy have a higher death rate than those with autism alone.

Autism spectrum disorders, a group of developmental disabilities, affect about one in 110 U.S. children, according to the CDC. Epilepsy, a brain disorder involving spontaneous seizures, affects about 3 million Americans, according to the Epilepsy Foundation.

Autism Patients With Epilepsy

Devinsky evaluated the records of 127 patients with autism and at least one epileptic seizure over a 20-year period. He looked at laboratory and clinical data from the patients who had been coming to the NYU Epilepsy Center.

He defined treatment-resistant as failing two trials of tolerated drugs to treat epilepsy.

Overall, Devinsky found that 33.9% of the patients had treatment-resistant epilepsy and 27.5% were seizure-free (no seizures during a 12-month period). The other 38.6% had insufficient information or infrequent seizures and were not placed into a category.

"We only have good follow-up data on two-thirds of the 127," he says. "Of those two-thirds, more than 50% have intractable epilepsy."

Those who were treatment-resistant reported seizure onset at an earlier age than those who were seizure-free. They also had more regression in developmental tasks. And they had more delays in motor and language skills.

Devinsky found that four patients who underwent epilepsy surgery had little or no improvement. Nine patients had another treatment, vagus nerve stimulation. Two of those had limited improvement and seven had no improvement in their epilepsy, he says.

"If a person with autism develops epilepsy and it's not easily contained with medication, he should seek consultation or care at an epilepsy center," Devinsky says.

If a child with autism has a seizure, he says, it's important to get an evaluation.

Autism and Epilepsy Linked, but Why?

The new research confirms what experts have suspected, says Solomon Moshe, MD, professor of neurology, neuroscience, and pediatrics and director of child neurology and clinical neurophysiology, Einstein College of Medicine and Montefiore Medical Center, Bronx, N.Y.

It also provides interesting data, he says. He reviewed the study findings for WebMD but was not involved in the study.

Experts can't explain the link between epilepsy and autism, Moshe says. "There may be a subset of genes that account for both the expression of autistic behavior and the seizure.”

The link is under study by experts, including a task force of the International League Against Epilepsy, says Moshe. He is president of the organization. The journal Epilepsia is published on behalf of the International League Against Epilepsy.

Until more is known, Moshe says, those with autism or their caregivers need to be aware that the two conditions can occur together.

The hope, he says, is to develop medication that could treat both.

Another researcher has found that vagus nerve stimulation (VNS) can help some with autism and epilepsy. "VNS can be a very safe adjunct in the treatment of epilepsy in kids both with and without autism," says Michael L. Levy, MD, PhD, a doctor at Children's Hospital of San Diego, University of California.

In his study, published last year in the Journal of Neurosurgery: Pediatrics, Levy looked at 77 children with autism spectrum disorder and epilepsy. He found they responded as well as other patients who did not have autism. They also had improvement in quality-of-life measures.

The nine children who had vagus nerve stimulation in the Devinsky study may be too few to reflect a benefit, he says.

''The study is important in that it shows how interlinked autism and epilepsy are," says Joseph Sirven, MD, chair elect of the professional advisory board of the Epilepsy Foundation. He reviewed the study findings. "Sadly, the epilepsy associated with autism appears to be of a severe variety."